Flex-rigid wiring board and method of manufacturing the same

ABSTRACT

A flex-rigid wiring board includes a flexible board including a flexible substrate and a conductor pattern formed over the flexible substrate, a non-flexible substrate disposed adjacent to the flexible board, an insulating layer including an inorganic material and covering the flexible board and the non-flexible substrate, the insulating layer exposing at least one portion of the flexible board, a conductor pattern formed on the insulating layer, and a plating layer connecting the conductor pattern of the flexible board and the conductor pattern on the insulating layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefits of priority to U.S.application Ser. No. 11/927,144, filed Oct. 29, 2007 and U.S.Application No. 60/863,396, filed Oct. 30, 2006. The contents of thoseapplications are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flexible wiring board having aflexible portion and a method of manufacturing the flexible wiringboard.

2. Discussion of the Background

A flex-rigid wiring board, a part of which has rigidity, and the otherpart of which has flexibility, is described, for example, in JapaneseUnexamined Patent Application Publication Nos. 2006-140213 and2006-100703, and PCT International Publication WO2004/093508.

A flex-rigid wiring board described in Japanese Unexamined PatentApplication Publication No. 2006-140213 has core boards which are rigidportions, a flexible board disposed adjacent to the core boards in ahorizontal direction, flexible adhesive layers laminated on the coreboards and the flexible board, wiring patterns formed on the flexibleadhesive layers located on the rigid portions, and blind vias and/orthrough-holes connecting the wiring patterns formed on individuallayers. In the structure described above, the flexible adhesive layer islaminated on the flexible board.

Japanese Unexamined Patent Application Publication No. 2006-100703describes a method for manufacturing a flex-rigid wiring board. In thatmethod, first, rigid boards each having a vertical wiring portion in aconnection region and a flexible board having connection terminalsformed at end portions are separately formed. Subsequently, theconnection regions of the rigid boards are each machined to form acut-off portion having a depth larger than the thickness of the flexibleboard, thereby forming steps. Next, the connection terminals of theflexible board are connected to the vertical wiring portions at thesteps.

A flex-rigid wiring board described in PCT International PublicationWO2004/093508 includes a rigid board and a flexible board which arebonded with an insulating adhesive interposed to form a unified body. Inaddition, connection electrode pads of the rigid and flexible boards areelectrically and physically connected to each other through with aconductor block and penetrating through the insulating adhesive. In theflex-rigid wiring board having the above structure, the flexible boardis disposed on one side of the rigid substrate, a via is formed by laserirradiation, and connection is formed by plating from the flexible boardside.

The contents of the above mentioned publications are incorporated hereinby reference in their entirety.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a flex-rigid wiringboard has a flexible board including a flexible substrate and aconductor pattern formed over the flexible substrate, a non-flexiblesubstrate disposed adjacent to the flexible board, an insulating layerincluding an inorganic material and covering the flexible board and thenon-flexible substrate, a conductor pattern formed on the insulatinglayer, and a plating layer connecting the conductor pattern of theflexible board and the conductor pattern on the insulating layer. Theinsulating layer is exposing at least one portion of the flexible board.

According to another aspect of the present invention, a flex-rigidwiring board has a flexible board including a flexible substrate and aconductor pattern formed over the flexible substrate, a non-flexiblesubstrate disposed adjacent to the flexible board, an insulating layerincluding an inorganic material and covering the flexible board and thenon-flexible substrate, the insulating layer exposing at least oneportion of the flexible board, a conductor pattern formed on theinsulating layer, and a via formed in the insulating layer andconnecting the conductor pattern on the insulating layer and theconductor pattern of the flexible board.

According to yet another aspect of the present invention, a flex-rigidwiring board includes a flexible board including a flexible substrateand a conductor pattern formed over the flexible substrate, anon-flexible substrate disposed adjacent to the flexible board, aninsulating layer including an inorganic material and covering theflexible board and the non-flexible substrate, the insulating layerexposing one or more portions of the flexible board, a conductor patternformed on the insulating layer, and a via formed in the insulating layerand connecting the conductor pattern on the insulating layer and theconductor pattern of the flexible board. The flexible board furtherincludes a protective layer covering the conductor pattern of theflexible board, and the via formed in the insulating layer includes aplating layer.

According to still another aspect of the present invention, a method ofmanufacturing a flex-rigid wiring board includes disposing a flexibleboard including a flexible substrate and a conductor pattern formed overthe flexible substrate and a non-flexible substrate adjacent to eachother, covering a boundary between the flexible board and thenon-flexible substrate with an insulating layer including an inorganicmaterial, providing a conductor pattern on the insulating layer, forminga via hole opening which passes through the insulating layer and reachesthe conductor pattern of the flexible board, and plating the via holeopening to form a via connecting the conductor pattern of the flexibleboard and the conductor pattern on the insulating layer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIGS. 1A and 1B are a side view and a plan view, respectively, of aflex-rigid wiring board according to one embodiment of the presentinvention;

FIG. 2 is a partly enlarged view of FIG. 1A;

FIG. 3 is a view showing a modification of the flex-rigid wiring boardshown in FIG. 2;

FIG. 4 is a side view of a flexible substrate;

FIGS. 5A to 5L are a flowchart illustrating a manufacturing method of aflex-rigid wiring board according to another embodiment of the presentinvention;

FIGS. 5A′, 5G′, 5K′ and 5L′ are views illustrating modified steps of themethod of manufacturing a flex-rigid wiring board shown in FIGS. 5A to5L;

FIGS. 5F″, 5G″ 5K″ and 5L″ are views illustrating other modified stepsof the method of manufacturing a flex-rigid wiring board shown in FIGS.5A to 5L;

FIGS. 6A to 6F are enlarged views illustrating the manufacturing methodof a flex-rigid wiring board, which is illustrated with reference toFIGS. 5A to 5L;

FIG. 7 is a view showing a modification of the flex-rigid wiring boardshown in FIG. 3;

FIG. 8 is a view showing another modification of the flex-rigid wiringboard shown in FIG. 3;

FIGS. 9A and 9B are views each showing a modification of the flex-rigidwiring board shown in FIG. 2;

FIGS. 10A and 10B are views each showing a modification of theflex-rigid wiring board shown in FIG. 3;

FIGS. 11A to 11F are views illustrating steps of a manufacturing methodof the flex-rigid wiring board shown in FIG. 10A;

FIGS. 12A to 12F are views illustrating steps of a manufacturing methodof the flex-rigid wiring board shown in FIG. 10B;

FIGS. 13A and 13B are view each showing a modification of the flex-rigidwiring board shown in FIG. 7;

FIGS. 14A and 14B are views each showing a modification of theflex-rigid wiring board shown in FIG. 8;

FIG. 15 is a view showing an example in which a wiring pattern is fannedout;

FIG. 16 is a view showing an example in which the strength is increasedby forming a part of a flexible substrate to have a large width; and

FIG. 17 is a view showing another example in which the strength isincreased by forming a part of a flexible substrate to have a largewidth.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

As shown in FIGS. 1A and 1B, a flex-rigid wiring board 10 according toone embodiment of the present invention has a first rigid board 11, asecond rigid board 12, and a flexible board 13 connecting the rigidboards 11, 12.

On the first and the second rigid boards 11, 12, appropriate circuitpatterns are formed. In addition, whenever necessary, for example,electronic elements, such as a semiconductor chip, are connected.

On the flexible board 13, a stripe wire (13 a) is formed to connect thecircuit patterns of the first rigid board 11 and the second rigid board12. Hence, the wire (13 a) connects the circuit pattern of the rigidboard 11 and the circuit pattern of the rigid board 12.

As for the structure of a connection portion of the flexible board 13with the rigid boards 11, 12, the connection portion between the rigidboard 11 and the flexible board 13 is describe in detail by way ofexample with reference to FIG. 2.

FIG. 2 is an enlarged cross-sectional view of an area represented byreference numeral 2 of FIG. 1A. As shown in the figure, the flexibleboard 13 has the structure in which a substrate 131, conductive layers132, 133, insulating films 134, 135, shield layers 136, 137, and coverlays 138, 139 are laminated.

The substrate 131 may be formed of an insulating flexible sheet, such asa polyimide sheet having a thickness of approximately 20 to 50 μm,preferably a thickness of approximately 30 μm.

The conductive layers 132, 133 may be formed on the front surface andthe rear surface of the substrate 131, respectively, so that the stripewire pattern (13 a) is formed. The conductive layers 132, 133 may beeach formed, for example, of a copper pattern having a thickness ofapproximately 5 to 15 μm.

The insulating films 134, 135 may be each formed, for example, of apolyimide film having a thickness of approximately 5 to 15 μm andinsulate the conductive layers 132, 133 from the outside.

The shield layers 136, 137 (also referred as “electromagnetic shieldlayers”) may be formed of conductive layers, such as cured films madefrom a silver paste, to shied electromagnetic noises to the conductivelayers 132, 133 from the outside and to shield electromagnetic noises tothe outside from the conductive layers 132, 133.

The cover lays 138, 139 may be each formed of an insulating film made,for example, of a polyimide film having a thickness of approximately 5to 15 μm, and insulate and protect the whole flexible board 13 from theoutside.

On the other hand, the rigid board 11 is formed of a first insulatinglayer 111, a non-flexible substrate 112, a second insulating layer 113,a first upper insulating layer 114, and a second upper insulating layer115, which are laminated to each other.

The non-flexible substrate 112 imparts rigidity to the rigid board 11and may be formed of a non-flexible insulating material such as a glassepoxy resin. The non-flexible substrate 112 is disposed apart from theflexible board 13 in a horizontal direction. The non-flexible substrate112 is formed to have a thickness approximately equivalent to that ofthe flexible board 13, for example, approximately 50 to 150 μm,preferably approximately 100 μm.

The first and second insulating layers 111, 113 are formed by curingprepregs. The first and the second insulating layers 111, 113 each havea thickness of approximately 50 to 100 μm, preferably approximately 50μm.

The above prepregs are preferably formed of a resin having low flowproperties. The prepregs as described above may be formed byimpregnating glass clothes (111 a, 113 a), each of which is an inorganicmaterial, with an epoxy resin, followed by thermal curing of the resinto increase the curing degree thereof beforehand. Furthermore, inorganicmaterials (111 b, 113 b), such as silica filler or glass filler, may beadded to the resin.

In addition, the prepregs described above can also be formed byimpregnating glass clothes with a resin having a high viscosity,impregnating glass clothes with a resin containing inorganic filler, forexample, silica filler, or by decreasing the amount of a resin to beused for impregnation of glass clothes.

The first and the second insulating layers 111, 113 cover the front andthe rear surface sides of the non-flexible substrate 112 and theflexible board 13 and partly expose the flexible board 13. In addition,the first and the second insulating layers 111, 113 are overlappedtogether with the cover lays 138, 139 which are at the surfaces of theflexible board 13.

The non-flexible substrate 112 and the first and second insulatinglayers 111, 113 form a core of the rigid board 11 to support the rigidboard 11 and also support and fix the flexible board 13 by sandwichingone end portion thereof.

The non-flexible substrate 112, the flexible board 13, and the first andsecond insulating layers 111, 113 form a space, and a resin 125 isfilled in this space. The resin 125 is, for example, a resin seepingfrom low-flow prepregs forming the first and second insulating layers111, 113 during the manufacturing and is integrally cured together withthe first and second insulating layers 111, 113. Hence, the resin 125also includes an inorganic material.

Furthermore, in a part of the second insulating layer 113 correspondingto a connection pad (13 b) of the wire 133 of the flexible board 13, avia opening (via hole or contact hole) 116 is formed.

In the flexible board 13, at a part corresponding to the via opening 116(part at which the connection pad (13 b) of the conductive layer (13 a)is formed), the shield layer 137 and the cover lay 139 of the flexibleboard 13 are removed. The via opening 116 penetrates the insulating film135 of the flexible board 13 and exposes the connection pad (13 b) ofthe conductive layer 133.

On the inner surface of the via opening 116, a conductive layer 117 (mayalso be referred as “vias,” “via hole conductor structure,” or “viacontact”) made by copper plating or the like is formed. The conductivelayer 117 (may also be referred as a via, a via hole conductorstructure, or a through hole conductor structure) is connected to theconnection pad (13 b) of the conductor layer 133 of the flexible board13 by plating. In addition, the via opening 116 is filled with a resin,such as a resin containing an inorganic material.

On the second insulating layer 113, an extending pattern 118 connectedto the conductive layer 117 is formed. The extending pattern 118 may beformed of a copper plating layer or the like.

In addition, at a front end of the second insulating layer 113, that is,at a position extending over a boundary between the flexible board 13and the non-flexible substrate 112, a copper pattern 124 isolated fromthe others is disposed. Hence, heat generated in the rigid board 11 iseffectively dissipated.

The first upper insulating layer 114 is disposed so as to be laminatedon the second insulating layer 113. The first upper insulating layer 114may be formed by curing a material containing an inorganic material,such as silica filler, glass filler, carbon fibers, or ceramic fibers,e.g., prepregs having glass clothes impregnated with a resin. By thestructure as described above, dropping impact resistance is improved.

In a manufacturing process of this flex-rigid wiring board, the viaopening 116 is filled with a resin containing an inorganic material,which is supplied from the prepregs.

In addition, on the first upper insulating layer 114, the second upperinsulating layer 115 is disposed. The second upper insulating layer 115may be formed by curing prepregs made of glass clothes impregnated witha resin containing an inorganic material such as silica filler or glassfiller.

In the first upper insulating layer 114 disposed on the secondinsulating layer 113, a via opening (first upper via opening) 119connected to the extending pattern 118 is formed. The via opening 119 isfilled with a conductor 120 (may also be referred to as “upper vias,”“upper via hole conductor structure,” or “upper via contact”) made ofcopper or the like. In addition, in the second upper insulating layer115 laminated on the first upper insulating layer 114, a via opening(second upper via opening) 121 connected to the via opening 119 isformed. The via opening 121 is filled with a conductor 122 (alsoreferred to as “vias,” “via hole conductor structure,” or “viacontact”). That is, by vias 120, 122 (may also be referred as “uppervia”), a filled buildup via is formed.

On the second upper insulating layer 115, a conductive pattern (circuitpattern) 123 is appropriately formed. The via 120 is also appropriatelyconnected to the above conductive pattern 123.

In addition, the structure of a connection portion between the rigidboard 12 and the flexible board 13 is similar to that of between therigid board 11 and the flexible board 13.

In the flex-rigid wiring board 10 having the above structure, the endportion of the flexible board 13 is sandwiched by the first and secondinsulating layers 111, 113 forming the rigid board 11 and is overlapped.

Furthermore, the connection pad (13 b) of the conductive layer 133 ofthe flexible board 13 and the conductive pattern 123 of the rigid board11 are connected to each other via the copper plating layer 117 (mayalso be referred as “via,” “via hole conductor structure,” or“through-hole conductor structure”) formed in the via opening 116 whichis formed in the second insulating layer 113 and the insulating film135.

Hence, when the flexible board 13 is bent, a stress applied thereto isnot transmitted to the connection portion (via opening 116 and the layer117) of the rigid board 11. As a result, a stress applied to theconnection portion between the rigid board 11 and the flexible board 13is small, and hence the reliability is high.

In particular, the insulating layers 111, 113 contain the inorganicmaterials (111 a, 111 b, 113 a, 113 b), such as glass clothes, silicafiller, glass filler, carbon fibers, and ceramic fibers. The inorganicmaterials mentioned above have high rigidity as compared to that of aresin which is an organic material. Hence, compared to the case in whichthe insulating layers 111, 113 are entirely formed of a resin, therigidity of the insulating layers 111, 113 is high. Accordingly, evenwhen the flexible board 13 is bent, the core is not substantiallydeformed. As a result, a stress is not likely to be transmitted to theconnection portion between the rigid board 11 and the flexible board 13.In addition, as the inorganic material, particularly, glass cloth ispreferable. Compared to other inorganic materials, the glass cloth canmost improve the rigidity of the insulating layers 111, 113.Accordingly, in the case in which the insulating layers 111, 113 containthe glass clothes (111 a, 113 b), even when the flexible board 13 isbent, the core is not deformed, and hence, a stress is not likely to betransmitted to the connection portion between the flexible board 13 andthe rigid board 11.

In addition, the conductive layer 133 of the flexible board 13 and thelayer 117 inside the via opening 116 are connected to each other byplating. Hence, the reliability of the connection portion is high.

Furthermore, in the via opening 116, the resin of the upper insulatinglayer 114 is filled. The via opening 116 is fixed and supported by theresin therein, and the connection reliability between the via 117 andthe conductive layer 133 is improved.

In addition, the end surfaces of the insulating layers 113, 111 at theflexible board side protrude further than the end surface of the upperinsulating layer 114 at the flexible board side. Hence, when theflexible board 13 is bent, a stress applied to the flexible board 13 isnot transmitted to the connection portion (the via opening 116 and thevia 117) of the rigid board 11. As a result, a stress applied to theconnection portion between the rigid board 11 and the flexible board 13is small, and hence the reliability is high.

In addition, the structure is formed so that the core portion of therigid board 11 restrains expansion and contraction of the flexible board13, which tends to expand and contract, in a horizontal direction.Hence, bending reliability and heat-resistance reliability are high.Since a flexible substrate portion of the flexible board 13 is exposedbetween the rigid boards 11, 12, compared to the case in which theentire structure is covered with an insulating resin or the like, whenbending is performed, a stress applied to wires or the like is small.

In addition, the flex-rigid wiring board 10 has the structure in whichthe end portion of the flexible board 13 is sandwiched by the first andsecond insulating layers 111, 113 of the rigid board 11. Hence, theinfluence of change in dimension of the flexible board 13 is small, andas a result, for example, the deviation in placement position of aconnection land (via 117) of the rigid board 11 can be decreased.Accordingly, the diameter of the via opening 116 can also be designed tobe small.

In addition, the insulating layers 111, 113 contain inorganic materials(111 a, 111 b, 113 a, 113 b), such as glass clothes, silica filler,glass filler, carbon fibers, and ceramic fibers. Compared to a resinwhich is an organic material, the inorganic materials mentioned abovehave a small coefficient of thermal expansion and make small expansionand contraction. Hence, compared to the case in which the insulatinglayers 111, 113 are entirely formed of a resin, the positional deviationof the connection land is small, and the connection land can be formedto be small.

In addition, in the rigid boards 11, 12, the flexible board 13 is notdisposed. Hence, reliability approximately equivalent to that of aconventional rigid board can be maintained. In addition, resistanceagainst a plating solution is high, and hence a general plating solutioncan be used. Since a flexible material is also not used for the rigidportion, heat resistance equivalent to that of a usual rigid portion canbe maintained.

Furthermore, since the flexible substrate 13 is partly used and iseffectively disposed, the manufacturing cost can be reduced.

The upper insulating layers 114, 115 may be formed of usual prepregs.The usual prepregs have good conformity with interlayer patterns whenbeing provided therebetween. Hence, insulation degradation caused, forexample, by generation of voids can be avoided. In addition, a finepattern, for example, (L/S=60/60, 50/50 μm) can be realized.Furthermore, material control can be performed in a restricted manner.

In addition, as the upper insulating layers 114, 115, a usual interlayermaterial (prepregs) may be used. Hence, in a manufacturing process, IVH(Interstitial Via Hole) including the via opening 116 can be filled witha resin forming the upper insulating layers 114, 115. As a result, aresin exclusively for filling the via is not required.

Since a glass epoxy substrate is used for the core portion of the rigidboard 11, dropping impact resistance is improved.

In this embodiment, in order to facilitate the understanding, only onthe upper surfaces of the rigid boards 11, 12, the conductive patternsare formed. However, the present invention is not limited to such anexample. For example, as shown in FIG. 3, conductive patterns may bedisposed at the lower sides of the rigid boards 11, 12.

In the structure shown in FIG. 3, a via opening 141 is formed in thefirst insulating layer 111 and the insulating film 134 of the flexibleboard 13. In the via opening 141, a conductive pattern 142 is formed andis connected to an extending pattern 143 formed on the first insulatinglayer 111. The conductive pattern 142 and the extending pattern 143 areformed by patterning a copper plating layer.

On the first insulating layer 111, third and fourth upper insulatinglayers 144, 145, which contain an inorganic material, are laminated. Inthe third and fourth upper insulating layers 144, 145, via openings 146,147 are formed. The via openings 146, 147 are filled with conductors148, 149 (also referred to as “vias,” “via hole conductor structure,” or“via contact”). On the upper insulating layer 145, a conductive pattern150 is formed.

Next, a method for manufacturing the flex-rigid wiring board 10 havingthe above structure will be described.

First, a method for manufacturing the flexible board 13 is describedaccording to one embodiment of the present invention.

Copper films are formed on two surfaces of the polyimide substrate 131processed into a predetermined size. Next, by patterning the copperfilms, the conductive layers 132, 133 having the wire patterns (13 a)and the connection pads (13 b) are formed.

On the polyimide substrate 131 and the two conductive layers 132, 133,the insulating films 134, 135 each made of a polyimide layer or the likeare formed. In addition, a silver paste is coated on the flexible board13 other than the end portion thereof and is then cured, so that theshield layers 136, 137 are formed.

Subsequently, the cover lays 138, 139 are formed so as to cover theshield layers 136, 137 located at the front surface and the rear surfacesides, respectively.

As described above, the flexible board 13 having the structure shown inFIG. 4 is formed. In this structure, the shield layers 136, 137 and thecover lays 138, 139 are formed at places other than those for theconnection pads (13 b).

Next, a method for bonding the rigid boards 11, 12 to the flexible board13 is described.

First, as shown in FIG. 5A, the first insulating layer 111, thenon-flexible substrate 112, and the second insulating layer 113, whichform the core of the rigid board 11, are aligned. In this case, thefirst and the second insulating layers 111, 113 are formed, for example,of low flow prepregs containing inorganic materials (111 a, 111 b, 113a, 113 b), and having a thickness of approximately 20 to 50 μm, and thenon-flexible substrate 112 is formed, for example, of a glass epoxysubstrate having a thickness of approximately 100 μm. The low flowprepregs as described above are formed, for example, by impregnating theglass clothes (111 a, 113 a), which are an inorganic material, with anepoxy resin added with the inorganic materials (111 b, 113 b), such assilica filler or glass filler, or by thermally curing of an epoxy resinadded with the inorganic materials (111 b, 113 b), such as silica filleror glass filler, beforehand to increase the curing degree.

In this embodiment, as shown in FIG. 2, the thickness of thenon-flexible substrate 112 and the thickness of the flexible board 13are preferably approximately equivalent to each other. According to thestructure described above, in a space present between the non-flexiblesubstrate 112 and the cover lay 139, the resin 125 containing theinorganic materials (111 b, 113 b) can be filled, and the flexible board13 and the non-flexible substrate 112 can be securely adhered to eachother.

In addition, since the resin 125 filled in the space is integrally curedwith the insulating layer 113, the periphery of the via opening 116 isfixed by the resin 125, and hence the connection reliability between thevia 117 and the conductive layer 133 is improved.

In the same manner as described above, a non-flexible substrate andfirst and second insulating layers, which form a core of the rigid board12, are aligned.

Furthermore, one end portion of the flexible board 13 is sandwichedbetween the first and second insulating layers 111, 113 of the rigidboard 11 for positioning, and the other end portion is disposed betweenthe non-flexible substrate and the first and second insulating layers ofthe rigid board 12. Furthermore, conductive films 161, 162 (alsoreferred as “copper foils”) made of copper or the like are disposed onthe top and the bottom of a structure thus formed. A separator may beprovided on the flexible board 13 before conductor films 161,162 isdisposed on and below these layers.

Next, as shown in FIG. 5B, the above structure is pressed underpressure. In this step, as shown by an enlarged view of FIG. 6A, theresin 125 containing the inorganic materials (111 b, 113 b), which isextruded from the prepregs forming the first and second insulatinglayers 111, 113, fills the space between the non-flexible substrate 112and the flexible board 13. As described above, since the space is filledwith the resin 125, the flexible board 13 and the non-flexible substrate112 can be securely adhered to each other.

The above pressure pressing may be performed, for example, by ahydraulic press apparatus under conditions in which the temperature, thepressure, and the press time are set to approximately 200° C., 40 kgf,and 3 hours, respectively.

Subsequently, for example, by heating the whole structure, the prepregsforming the first and second insulating layers 111, 113 and the resin125 are cured and are integrated together. In this step, the cover lays138, 139 of the flexible board 13 and the resin of the first and secondinsulating layers 111, 113 are overlapped. When the resin of theinsulating layers 111, 113 is overlapped, the periphery of the viaopening 116 is fixed by the resin, and the connection reliabilitybetween the via 117 and the conductive layer 133 is improved.

Next, for example, by irradiation of CO₂ laser from a CO₂ laserprocessing device, IVH (Interstitial Via Hole) 163 is formed as requiredas shown in FIG. 5C. In this case, as shown by an enlarged view of FIG.6B, the via openings 116, 141 are also formed to connect the wire layers132, 133 of the flexible board 13 to the rigid boards 11, 12.

Subsequently, as shown in FIG. 5D, the entire surface of the structureis processed by copper plating. This copper plating and the existingcopper patterns 161, 162 are integrated together, and hence a copperfilm 171 is formed over the entire surface of the board. As shown inFIG. 6C, the copper film 171 is also formed inside the via openings 116,141. In this step, the flexible board 13 is covered with the copperfoils 161, 162 and hence is not directly brought into contact with aplating solution. Hence, the flexible board 13 is not damaged by aplating solution.

Subsequently, as shown in FIG. 5E, the copper film 171 located at theboard surface is patterned. By this step, the vias 117, 142 connected tothe conductive layers 132, 133 of the flexible board 13 and theextending patterns 118, 143 are formed. In this step, as shown in FIG.6D, the copper foil 171 is allowed to remain at the edge portions of thefirst and second insulating layers 111, 113.

Next, as shown in FIG. 5F, on the top and bottom of a resultingstructure, the first and third upper insulating layers 114, 144 mat bedisposed. The first and third upper insulating layers 114, 144 may beformed, for example, of prepregs made of glass clothes, which are aninorganic material, impregnated with a resin containing an inorganicmaterial such as silica filler or glass filler. The via openings 116,141 are filled with the resin forming the prepregs.

Subsequently, for example, by curing the resin of the prepregs andinside the via openings by heating, the first and third upper insulatinglayers 114, 144 are solidified. Then, via openings 119, 144 are formedin the first and third upper insulating layers 114, 144, and by copperplating or the like, the via openings 119, 144 are filled with aconductive material. Alternatively, a conductive paste (for example, athermosetting resin containing conductive particles) may be filled inthe via openings 119, 114 by screen printing or the like, followed bycuring.

Next, as shown in FIG. 5G, on the top and bottom of the entire board,the second and fourth upper insulating layers 115, 145 are disposed. Thesecond and fourth upper insulating layers 115, 145 may be formed, forexample, of usual prepregs made of glass clothes, which are an inorganicmaterial, impregnated with a resin containing an inorganic material suchas silica filler or glass filler. Before the second and fourth upperinsulating layers 115,145 are formed, a separator may be disposed in anopening formed in the first and third upper insulating layers 114, 144.

Subsequently, for example, by curing the resin of the prepregs byheating, the second and fourth upper insulating layers 115, 145 aresolidified.

Furthermore, via openings 121, 147 are formed in the second and fourthupper insulating layers 115, 145, and by copper plating or the like, thevia openings 121, 147 are filled with a conductive material.Alternatively, a conductive paste (for example, a thermosetting resincontaining conductive particles) may be filled in the via openings 121,147 by screen printing or the like, followed by curing. When the sameconductive paste material is filled in the via openings 121, 147, theconnection reliability is improved when a thermal stress is applied tothe vias 122, 149 (also referred as “upper vias”).

Furthermore, as required, as shown in FIG. 5H, resin provided withcopper foil sheets (Resin Copper Film; RCF) 172, 173 may be disposed asthe outermost layers of the board, followed by pressing.

Subsequently, the entire structure is heated, so that the resin iscured.

Then, as shown in FIG. 5I, via openings 174, 175 are formed in the RCFs172, 173. Next, by copper plating or the like, the via openings 174, 175are filled with a conductive material. In addition, as required, thecopper foil located at the surface is patterned to form a conductivepattern.

Next, as shown in FIGS. 5J and 6E, bonding portions of the flexibleboard 13 with the rigid boards 11, 12 are irradiated with laser beam158, such as CO₂ laser, generated from a laser processing device, sothat the upper insulating layers 114, 115, 144, 145, and the resin withcopper foil sheets (RCFs) 172, 173 are cut, using the copper foil 171formed on the edge portions of the cores of the rigid boards 11, 12 as astopper. In this step, the energy or the irradiation time is adjusted soas to cut the copper foil 171 used as the stopper to a certain extent.

Accordingly, as shown in FIG. 5H, a structure 181 on the flexible board13 is separated from the others.

Next, as shown in FIG. 5L, the structure 181 is removed by peeling offfrom the flexible board 13. The copper foils 161, 162 (see FIG. 5B),from which the remaining copper foil 171 is formed, are simply pressedon the cover lays 138, 139 and are not fixedly bonded thereto. In thesame manner as described above, the copper foil 171 is also not fixedlybonded to the flexible board 13. Hence, when the structure 181 isremoved, the copper foil 171 is also removed.

As described above, parts of the copper foil 171, which are not coveredby other components, are removed. Hence, at the edge portions of thefirst and second insulating layers 111, 113, the copper foils 124, 151,which are covered with the prepregs 113, 144, remain.

As described above, the end portions of the flexible board 13 are heldby the core portions (the first and second insulating layers 111, 113)of the rigid boards 11, 12, and in addition, lands of the rigid boards11, 12 and connection pads of the flexible board 13 are connected toeach other by plating, thereby forming the flex-rigid wiring board 10.

According to the structure described above, plating on polyimide of theflexible board 13 is not required, and hence the connection reliabilityis ensured.

In addition, RCF can be used as the outermost layers of the rigid boards11, 12. Hence, similar reliability and dropping impact resistance asthose of a conventional rigid board is ensured.

In this manufacturing method, in order to form the core layers of therigid boards 11, 13, prepregs made of a resin having low flow propertiesare used. However, for other than the core layers, usual prepregs may beused, IVH filling is not required, and voids are also not liable to begenerated.

Furthermore, since only the bending portion is formed of the flexibleboard, the stability is improved.

Since openings are formed in multiple layers by laser processing afterthe external layers are formed, the manufacturing cost is reduced.

In addition, since openings are formed in multiple layers by laserprocessing after the external layers are formed, the accuracy of theopening in the flexible board is high.

In addition, since the core portions of the rigid boards 11, 12 areformed of a glass epoxy substrate, the dropping impact resistance isimproved.

A method for manufacturing the flex-rigid wiring board 10 is not limitedto those steps referred in FIGS. 5A to 6L. For example, referring toFIG. 5A′, a separator 291 may be provided in a gap (113 a) formed in thesecond insulating layer 113. The separator 291 may be, for example, acured prepreg or a polyimide film. Also, an adhesive may be providedbetween the separator 291 and the copper film 171.

In such a case, through the steps shown in FIGS. 5B to 5F, the copperfilm 171 and the upper insulating layers 114, 115 may be formed over theseparator 291 as shown in FIG. 5G′. Subsequently, through the stepsshown in FIGS. 5H to 5I, the copper film sheet with resin (Resin CopperFilm or RCF) 173 is provided over the upper insulating layer 115, andthe via opening 174 is formed and filled with conductive material. Then,the boundary between the upper insulating layer 113 and the separator291 is cut by the laser beam 158, using the copper film 171 as astopper. At this time, the energy or irradiation time of the laser beam158 may be adjusted such that the copper film 171 is cut appropriatelyto some extent. As such, a structure 181 over the flexible board 13 isseparated as shown in FIG. 5K′. Then, the structure 181 may be torn offand removed from the flexible board 13 as shown in FIG. 5L′. Theseparator 291 makes easier to tear off and remove the structure 181 fromthe flexible board 13. Also, the separator 291 supports the copper film171 and prevents a plating solution from seeping into the gap (113 a)between the flexible board 13 and the copper film 162 and the copperfilm 171 from being torn.

Also, referring to FIGS. 5F″, 5G″, 5K″ and 5L″, another method formanufacturing the flex-rigid wiring board 10 is described below as amodification from the steps shown in FIGS. 5A to 6L. In thismodification, after the separator 291 is provided, the steps describedin FIGS. 5B through 5F are carried out. Then, using a laser, a cut line292 may be formed in a portion of the upper insulating layer 114 abovethe separator 291 as shown in FIG. 5F″. Thereafter, the upper insulatinglayer 115 is provided over the upper insulating layer 114. However, inthe place of a portion of the upper insulating layer 115, a separator293 having one edge portion reaching over the cut line 292 is providedas shown in FIG. 5G″. Subsequently, the resin bearing copper film sheet173 is provided over the upper insulating layer and the separator 293 bycarrying out the steps described in FIGS. 5H and 5I, a via opening isformed in the upper insulating layer 115, and copper plating isconducted. Then, using a laser, cut lines 294, 295 are formed over oneedge portion of the separator 291 and over the other edge portion of theseparator 293 as shown in FIG. 5K″. Finally, as shown in FIG. 5L″, astructure 296 defined by the cut line 294, the separator 291, the cutline 292, the separator 293 and the cut line 295 is removed. With such astructure, a portion or portions which do not contribute to theformation of circuitry may be removed and the volume of a wiring boardmay be reduced.

In the above, the modifications concerning the manufacturing stepsrelated to the rigid board 12 are described. However, such modificationsmay be applied to the manufacturing steps of the rigid board 11 or bothof the rigid boards 11, 12. Also, in the examples described above, themodifications describe the manufacturing steps concerning the upperportions of the flex-rigid wiring board 10. However, such modificationsmay be applied to the lower portions of the flex-rigid wiring board 10or the flex-rigid wiring board 10 as a whole.

The flex-rigid wiring board 10 according to one embodiment of thepresent invention is described above; however, the present invention isnot limited to such an example.

For example, the materials, sizes, number of layers described above, andthe like may be modified appropriately.

For example, in the above embodiment, the resin 125 and the resinforming the first and second insulating layers 111, 113, the upperinsulating layers 114, 115, 144, 145 are described as a resin containingan inorganic material. However, the present invention is not limited tothat described above, and for example, as a resin forming the upperinsulating layers 114, 115, 144, 145, a resin containing no inorganicmaterials may be used.

Furthermore, when the first and second insulating layers 111, 113 havethe glass clothes (111 a, 113 a), the resin thereof may not contain aninorganic material.

The materials, forms (clothes, filler, particles, and the like),addition amounts, and content ratios of the inorganic materialscontained in the individual components may be appropriately selected anddetermined in accordance with rigidity, strength, coefficient of thermalexpansion, and the like required for the components.

In addition, as shown in an example of FIG. 7, the via openings 116, 141may be filled with a conductive material such as a plating metal. Whenthe via openings 116, 141 are not fully filled with a resin, voids maybe present inside the via openings 116, 141. In this case, when heat isapplied to the flex-rigid wiring board 10, the connection reliability ofthe vias may be degraded in some cases due to expansion of the voids. Asshown in FIG. 7, when the via openings 116, 141 are filled with aplating metal, the connection reliability of the vias 117, 142 isimproved when heat is applied thereto.

As is the case described above, conductive patterns (circuit patterns)191, 192 may be formed on the non-flexible substrate 112 to be connectedto appropriate portions.

In addition, conductive patterns (circuit patterns) 193, 194 may beformed on the upper insulating layers 114, 144 to be connected toappropriate portions.

The conductive patterns 191, 143, 193, 150 are connected to each otherthrough the vias 148, 149 and other appropriately formed vias. In thesame manner as described above, the conductive patterns 192, 118, 194,123 are connected to each other through the vias 120, 122 and othervias. Furthermore, through the via formed in the via opening 163, theconductive patterns 123, 150 are also connected to each other.

In this embodiment, the first and second insulating layers 111, 113,which sandwich the end portion of the flexible board 13, may be formedfrom RCF. In addition, the first and third upper insulating layers 114,144 and the second and fourth upper insulating layers 115, 145 may beformed of RCF. Such a structure allows the number of manufacturing stepsto be reduced.

In this embodiment, the thickness of the flexible board 13 is set to beapproximately equivalent to that of the non-flexible substrate 112;however, the present invention is not limited to such an example. Forexample, as shown in FIG. 8, the thickness of the flexible board 13 maybe formed smaller than that of the non-flexible substrate 112. In thiscase, a space formed between the flexible board 13, the non-flexiblesubstrate 112, and the first and second insulating layers 111, 113 isfilled with an appropriate resin, such as a resin which seeps from theinsulating layers 111, 113 or a resin which is provided beforehand inmanufacturing for height adjustment. Since the space is filled with theresin 125, the flexible board 13 and the non-flexible substrate 112 aresecurely adhered to each other.

In addition, those resins are integrally cured and solidified togetherby heating during manufacturing. As described above, since the resins ofthe insulating layers 111, 113 are overlapped, and the resin 125 isfurther integrally cured and solidified, the peripheries of the viaopenings 116, 141 are fixed by the resins, the connection reliability ofthe vias 117, 142 with the conductive layer 133, 132 are improved.

In the embodiment described above, the first insulating layer 111contains the glass clothes (111 a) and the inorganic material (111 b),and the second insulating layer 113 contains the glass clothes (113 a)and the inorganic material (113 b). However, as for the flex-rigidwiring board 10 shown in FIG. 2, for example, the structure may beformed as shown in FIG. 9A in which the first and second insulatinglayers 111, 113 contain the glass clothes (111 a, 113 a) and contain noinorganic materials (111 b, 113 b). In addition, as shown in FIG. 9B, astructure may also be formed such that the first and second insulatinglayers 111, 113 contain the inorganic materials (111 b, 113 b) butcontain no glass clothes (111 a, 113 a).

Furthermore, as for the flex-rigid wiring board 10 shown in FIG. 3, forexample, as shown in FIG. 10A, the first and second insulating layers111, 113 may contain the glass clothes (111 a, 113 a), respectively, butmay not contain the inorganic materials (111 b, 113 b). In addition, asshown in FIG. 10B, the first and second insulating layers 111, 113 maycontain the inorganic materials (111 b, 113 b), respectively, but maynot contain the glass clothes (111 a, 113 a).

The flex-rigid wiring board 10 having the structure shown in FIG. 10A ismanufactured, for example, by the steps shown in FIGS. 5A to 5L andFIGS. 11A to 11F. This manufacturing method is similar to that describedwith reference to FIGS. 5A to 5L and FIGS. 6A to 6F except that as thefirst and second insulating layers 111, 113, insulating layers(prepregs) which contain the glass clothes (111 a, 113 a) but contain noinorganic materials (111 b, 113 b) are used.

In addition, the flex-rigid wiring board 10 having the structure shownin FIG. 10B is manufactured, for example, by the steps shown in FIGS. 5Ato 5L and FIGS. 12A to 12F. This manufacturing method is similar to thatdescribed with reference to FIGS. 5A to 5L and FIGS. 6A to 6F exceptthat as the first and second insulating layers 111, 113, insulatinglayers (prepregs) which contain no glass clothes (111 a, 113 a) butcontain the inorganic materials (111 b, 113 b) are used.

Furthermore, the flex-rigid wiring board 10 shown in FIG. 7 may beformed, for example, of the first and second insulating layers 111, 113which contain the glass clothes (111 a, 113 a) but contain no inorganicmaterials (111 b, 113 b). In addition, as shown in FIG. 13B, the firstand second insulating layers 111, 113 may contain the inorganicmaterials (111 b, 113 b), respectively, but may not contain the glassclothes (111 a, 113 a).

Furthermore, the flex-rigid wiring board 10 shown in FIG. 8 may beformed, for example, of the first and second insulating layers 111, 113which contain the glass clothes (111 a, 113 a) but contain no inorganicmaterials (111 b, 113 b), as shown in FIG. 14A. In addition, as shown inFIG. 14B, the first and second insulating layers 111, 113 may containthe inorganic materials (111 b, 113 b), respectively, but may notcontain the glass clothes (111 a, 113 a).

In the embodiments described above, as the inorganic materials containedin the insulating layers 111, 113, the glass clothes (111 a, 113 a), andsilica filler or the glass filler (111 b, 113 b) are described by way ofexample. The insulating layers 111, 113 may contain an inorganicmaterial other than those described above. For example, the insulatinglayers 111, 113 may contain silica particles, glass particles, carbonfibers, ceramic fibers, and the like.

Furthermore, the upper insulating layers 114, 115, 144, 145 alsopreferably contain inorganic materials such as glass clothes, silicafiller, glass filler, and the like.

In addition, the wire patterns formed on the rigid boards 11, 12 and theflexible board 13 are not limited to those shown in FIG. 1, and as shownin FIG. 17, for example, a wire pattern may be formed so as to be fannedout from the flexible board 13 toward the rigid boards 11, 13. That is,the pitch of the connection portion (13 b) may be set larger than thepitch of the wire (13 a) of the flexible board 13. Accordingly, a largernumber of wires may be disposed on the flexible board 13, and as aresult, a flex-rigid wiring board having a high wire density can beformed.

In addition, in order to increase the strength of boundary portionsbetween the flexible board 13 and the rigid boards 11, 12, as shown inFIGS. 18 and 19, for example, the flexible board 13 may be formed tohave a partly larger width. Accordingly, the bonding areas of theflexible board 13 and the rigid boards 11, 12 are increased, and as aresult, the connection reliability of the vias is improved.

For example, in the example shown in FIG. 18, the end portion of theflexible board 13 is enlarged, so that the areas of parts to be fixed tothe rigid boards 11, 12 are increased. Accordingly, the strength of theend portions of the flexible board 13 is increased, and hence thebending resistance is improved.

In addition, in the example shown in FIG. 19, protrusions are formed atpositions in which the flexible board 13 is bent repeatedly (forexample, positions which correspond to the end portions of the rigidboards 11, 12), so that the strength at the positions in which bendingis repeatedly performed is increased.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A flex-rigid wiring board comprising: aflexible board comprising a flexible substrate and a conductive layerformed over the flexible substrate, the conductive layer having aconductor pattern and a plurality of connection portions connected tothe conductor pattern; a non-flexible substrate disposed adjacent to theflexible board; an insulating layer comprising an inorganic material andcovering the flexible board and the non-flexible substrate, theinsulating layer exposing at least one portion of the flexible board; aconductive layer formed on the insulating layer and including aconductor pattern; and a via hole conductor formed in the insulatinglayer and connecting the conductive layer on the insulating layer andthe conductive layer of the flexible board at the plurality ofconnection portions; and a second insulating layer covering the flexibleboard and the non-flexible substrate and exposing the at least oneportion of the flexible board, wherein the insulating layer coverssurfaces of the flexible board and the non-flexible substrate on a firstside and the second insulating layer covers surfaces of the flexibleboard and the non-flexible substrate on a second side opposite to thefirst side.
 2. The flex-rigid wiring board according to claim 1, whereinthe plurality of connection portions are provided at a pitch greaterthan a pitch of the conductor pattern of the flexible board.
 3. Theflex-rigid wiring board according to claim 1, further comprising: anupper insulating layer formed on the insulating layer and comprising aninorganic material; an upper conductive layer formed on the upperinsulating layer; and an upper via formed in the upper insulating layer,the upper via connecting the conductive layer on the insulating layerand the upper conductive layer, wherein the insulating layer has an endsurface protruding from an end surface of the upper insulating layerover the flexible board.
 4. The flex-rigid wiring board according toclaim 1, further comprising: an upper insulating layer formed on theinsulating layer and comprising an inorganic material; an upperconductive layer formed on the upper insulating layer; an upper viaformed in the upper insulating layer, the upper via connecting theconductive layer on the insulating layer and the upper conductive layer;and a resin layer comprising a resin and disposed on the insulatinglayer, wherein the via is filled with the resin of the resin layer. 5.The flex-rigid wiring board according to claim 1, wherein the secondinsulation layer comprises an inorganic material.
 6. The flex-rigidwiring board according to claim 1, wherein the inorganic material in thesecond insulation layer comprises at least one of glass cloth, silicafiller, glass filler, carbon fiber and ceramic fiber.
 7. A flex-rigidwiring board comprising: a flexible board comprising a flexiblesubstrate and a conductive layer formed over the flexible substrate; anon-flexible substrate disposed adjacent to the flexible board; aninsulating layer comprising an inorganic material and covering theflexible board and the non-flexible substrate, the insulating layerexposing at least one portion of the flexible board; a conductive layerformed on the insulating layer; a via hole conductor formed in theinsulating layer and connecting the conductive layer on the insulatinglayer and the conductive layer of the flexible board, the via holeconductor comprising a plating layer; and a second insulating layercovering the flexible board and the non-flexible substrate and exposingthe at least one portion of the flexible board, wherein the flexibleboard further comprises a cover layer protecting the flexible board, aspace between the non-flexible substrate and the cover layer and aperiphery of the via hole conductor are filled with a resin materialcomprising an inorganic material, and the insulating layer coverssurfaces of the flexible board and the non-flexible substrate on a firstside and the second insulating layer covers surfaces of the flexibleboard and the non-flexible substrate on a second side opposite to thefirst side.
 8. The flex-rigid wiring board according to claim 7, whereinthe flexible board including the cover layer has a thicknessapproximately equivalent to a thickness of the non-flexible substrate.9. The flex-rigid wiring board according to claim 7, wherein the resinmaterial comprises a resin cured integrally with the insulating layer.10. The flex-rigid wiring board according to claim 7, wherein theflexible board further comprises a shield layer which shields anelectromagnetic wave, and the shield layer is formed on the insulatinglayer.
 11. The flex-rigid wiring board according to claim 10, whereinthe cover layer is formed on the shield layer.
 12. The flex-rigid wiringboard according to claim 10, wherein the cover layer is in contact withthe insulating layer.
 13. The flex-rigid wiring board according to claim7, wherein the second insulation layer comprises an inorganic material.14. The flex-rigid wiring board according to claim 7, wherein theinorganic material in the second insulation layer comprises at least oneof glass cloth, silica filler, glass filler, carbon fiber and ceramicfiber.